Top: latest results from Tevatron – cross-section and mass

Top: latest results Top: latest results from from

Tevatron – Tevatron – cross-section and cross-section and

mass mass Mircea N. Coca

University of Rochester, NY- CDF

For the CDF and D0 collaborations

FPCP 2003, Paris, June

June 6th, 2003 Mircea Coca, U of Rochester - CDF 2

OutlineOutlineTevatron StatusThe upgrades of the CDF and D0 detectorsTop Production and Decay Top Physics Program for Run IIFirst Cross-Section Measurements at

1.96 TeV, in the Dilepton and Lepton+jets channelsTop Mass Measurements in CDF (Run II) and D0 (Run I)Top Physics Prospects


Tevatron Upgrades/StatusTevatron Upgrades/StatusRun II upgrades

ECM increase from 1.8 → 1.96 TeV→larger cross sectionsHigher luminosity Run I peak:2.4x1031 cm-2 s-1

Run II goal:3–4x1032cm-2 s-1

Run II peak:4.7x1031 cm-2 s-1

Analysis-quality data accumulated by Jan ‘03

CDF: 72.0 pb-1 ( 57.5 pb-1 with silicon) D0: 30 - 50 pb-1

Immediate goal for accelerator:

Deliver 225 pb-1 in FY 2003

Run IIa goal: 2 fb-1

Integrated Luminosity

Commissioning

Winter ‘03

Peak Luminosity


CDF and D0 Detectors CDF and D0 Detectors UpgradesUpgrades

Tracking: Expanded silicon coverage

New drift chamber (COT)

Extended lepton-ID: ||>1.0 →2.0

End Plug calorimeter

Expanded muon coverage

New Inner tracking silicon tracker, fiber tracker2T superconducting solenoid

Upgraded system for better -ID

CDFD0


Top Production and DecayTop Production and Decay

In proton-antiproton collisions, at 1.96 TeV,

top quarks are primarily produced in pairs

single top production: smaller rate (pblarge backgrounds

not observed yet

tt increased by 30% with the CM energy increase from 1.8 →1.96 TeV

Br(tW+b) ~100% in SM

Based on the W decay modes →3 experimental signatures:

~85 % ~15%

(1) Dilepton Very small backgrounds, but very small rate

(2) Lepton+Jets Manageable backgrounds and good rate

(3) All Jets Large QCD Background

W-

b

W+

b

q

q

lb

lb

jj

b

lb

jj

lb

b

jj

b

b

jj

W Decay Mode

g

t

t

(3)(2)(1)

-

-


Top Physics in Run IITop Physics in Run IIRun I: discovery mode

( Fermilab 1995) → crude look

at top’s properties Run II: precision mode→

we hope to answer fundamental questions:

Why is the top so heavy?Is the third

generation special?Is top involved

in EWSB? Is the top the liaison

to new physics?

Production cross-sectionResonance production

Production kinematics

Top Spin Polarization

CP violation

Anomalous Couplings

p

p t

b

W

q

q’

t b

W+

l

X

Top MassW helicity

|Vtb|

Branching Ratios

Rare/non SM Decays (eg: t→Zc/c, t→H+b)

Top Spin

Top Charge

Top Width

_ _

_

_


Production Cross-Sections Production Cross-Sections measurement:

benchmark measurements test of perturbative QCDprobe for physics beyond SM non-SM production, X ttnon-SM decay, t XbSUSY models with a tt-like signal

Higgs production (WH,ZH) is a background and the opposite

Run I: Run IIa (2fb-1): Theoretical cross-section:

To estimate signal contribution we use 7 pb

At NLO @ s=1.96 TeV for Mtop = 175 GeV: hep-ph/0303085

(Mangano et al)pbtt

71.088.07.6

tt

tt/tt ~26 %tt/tt ~ 7 %

Nobs -Nbck

A . Ltt

Acceptance Luminosity


in the Dilepton Decay in the Dilepton Decay Mode Mode

2 high-ET, isolated leptons (e, )

to be includedfor the future

large missing energy ET

D0: Raised ET cut in Z window

CDF: Veto Z-mass window events for ee, at least 2 jets with large ET

large transverse energy flow

HT =(ETleptons ,ET

jets)

Backgrounds

WW/WZ, Z/→ determined from Monte Carlo (MC) Z/*→ee, from data+MCW+jets, QCD Heavy Flavor from data

tt

jet

jet

b

b

p p

E T

jet

jet

b

b

pp p

E TE T

Event Selection


Dilepton Channel (ee, Dilepton Channel (ee, ee))

Source ee (events) ( events) e (events) L (pb-1)

48.0

42.6

33.0

Background

1.00 0.49

0.60 0.01

0.07 0.01

Signal

0.25 0.02

0.30 0.04

0.50 0.01

Run II data

4

2

1

tt

pblumsysstattt )()()(9.29 0.30.3

1.141.6

0.217.15

Run II

Preliminary:


ee+2 jets Top Candidate +2 jets Top Candidate

ET(e+) = 20.3 GeV pT(-) = 58.1 GeV/c ET

jet(1) = 141.0 GeV ET

jet(2) = 55.2 GeV ET = 91 GeV HT (e) = 216 GeV

e+

-

jet

jet

ET

Longitudinal View

Transverse View


Dilepton ChannelDilepton ChannelSource ee (events) ( events) e (events) Background

0.10 0.06

0.09 0.05

0.10 0.04

Signal

0.47 0.05

0.59 0.07

1.44 0.16

Run II data

1

1

3

Data

sample

luminosity:

72 pb-1

tt

Run II Preliminary:

Missing energy ET (GeV)Missing energy ET (GeV)

Eve

nts

pb 0.8(lum)1.5(syst)5.9(stat)13.2 tt

l

epto

ns


Kinematics of Dilepton CandidatesKinematics of Dilepton Candidates

Run 1L = 109 pb-1

1.8 TeV9 events

Run 2 PreliminaryL= 72 pb-1

1.96TeV5 events

Events with very large missing ET in Run 1


Lepton+JetsLepton+JetsEvent Pre-Selection

Further selections to reduce the background

b

b

p p

E T

jet

jet

jet

jet

A high PT isolated, charged lepton (e, ), large missing ET ( undetected)

Large jet multiplicity ( ≥ 3 )

Cosmic ray, electron conversion removal, dilepton veto, Z boson veto.

topological: ≥ 4 jets (DØ)

b jets with Soft Lepton Tag (SLT)≥ 3 jets, ≥ 1 SLT tag (DØ)

b jets with displaced vertex (SECVTX) ≥ 3 jets, ≥ 1 b tag (CDF) B-Jet with SLT

B-Jet with SECVTX

tt


Lepton+Jets TopologicalLepton+Jets Topological Event Pre-Selection

Preselect a sample enriched in W events

an EM object or with large PT and large missing energy Veto soft ’s in sample, veto dilepton events

Backgrounds

QCD multi-jets evaluated from data vs.Njets

e+jets: due to fake jets (and )

+jets: due to heavy flavor decays

W multi-jets background in the 4 jet bin estimated using data by Berends scaling law before topological cuts

DØ Run II Preliminary

)(

))1((

jets

jets

nW

nW

tt


Results for Topological Results for Topological AnalysisAnalysis

Source e+jets +jets L (pb-1)

49.5

40.0

Background

2.7 0.6

2.7 1.1

Signal

1.8

2.4

Run II data

4

4

Topological Selection

≥ 4 jets (|| < 2.5() or

|| < 2.0(e), pT >15 GeV)

Aplanarity >0.065

HT(ETjets) >180 GeV (e)

HT(ETjets+pT

W)>220GeV ()

QCD background estimation

QCD


Lepton+Jets with an SLT Lepton+Jets with an SLT tagtag

Event Selection

preselection as for topological tt

≥ 3 jets

softer topological cuts: HT(ET

jets)> 110 GeV

Aplanarity > 0.04

soft inside a jet

(b→, b→c→)

Backgrounds

QCD and W+jets determined from data

Source e+jets +jets L (pb-1)

50

40

Background

0.2 0.1

0.7 0.4

Expected Signal

0.5

0.8

Run II data

2

0

tt


1.46.2

3.44.3

Lepton+jets channels (SLT + Topological) combined

Run IIPreliminary:


Lepton+jets with a SECVTX-Lepton+jets with a SECVTX-tagtag

Event Selection

preselect a sample enriched in W events as already mentioned

≥ 3 jets with ET>15 GeV

≥ 1 jet with secondary vertex tag (SECVTX)

A jet is tagged as b jet if it has at least 2 good tracks and the displacement Lxy satisfies Lxy/xy >3 (typical xy~150 m, while Lxy~3 mm)

SecondaryVertex

+L+Lxyxy

d0

Jet axisPrimaryVertexPrompt

Tracks

(event tag) = 45 1 5 %

Probability of tagging a tt event:

tt


Backgrounds EstimationBackgrounds Estimation

Mistags:from # tagged jets with Lxy<0 in inclusive jet data W+heavy flavor:

from W+jets data, b tag rate and flavor composition Non W:

from data WW, WZ, Z→single top:

from Monte Carlo simulation

Backgrounds Jet Multiplicity for the background events and the data

1 and 2 jet bins are used as a control sample, the top events are in >= 3 jet bins15 Candidates in ~ 57.5 pb-1 control signal


Lepton+jets - SECVTX-Lepton+jets - SECVTX-taggingtagging

pb 0.3(lum)0.8(sys)1.9(stat)5.3)tσ(t

tt

Source W+1jet W+2 jets W+3jets W+4jets Expected Bkgr+Signal

34.0 ± 5.0

18.7 ± 2.4

7.4 ± 1.4

7.6 ± 2.0

Run II data

31

26

7

8

Run II

Preliminary:

Data

sample

luminosity:

57.5 pb-1

*


A “golden” lepton+jets A “golden” lepton+jets candidatecandidate

µ

Jet1

Jet2Lego viewJet3

Jet4

tt l+jet candidate: Nov 02 2002

run: 153693 event: 799494

+ 4 jets, with 2 SECVTX b-tags

SECVTX tag

SECVTX tag

Event primary vertex


Top Cross-Sections Summary Top Cross-Sections Summary D0 Preliminary

D0: All channels combined Run II Preliminary:


3.65.3

5.46.3


Top Mass: Lepton+jets Top Mass: Lepton+jets Event Selection

Select ≥4 jet events, similar tott analysis, except no requirement for a jet to be b-tagged

Each event→up to 24 solutions consistent with a top decay:

12 different jet-partons assignments

Every combination has two solutions for the longitudinal momentum

Impose Mt=Mt , M(j,j)=M(l,)=MW

PDG: MW, W, t

2-C fit applied, chose the event top mass corresponding to the lowest iffParameterized templates of top masses (150, 200) GeV and bkgd Continuous likelihood to extract top mass and statistical uncertainty

W+

W-

t

t

b-jet

b-jet

jet

jet

X

Reconstruction Method

5 vertices: 20 constraints


Systematic uncertainty summary

Top Mass MeasurementTop Mass Measurement33 candidates after event selection

8 events with a b tagged

CDF Run 1 combined: Mtop = 176.1 ± 6.5 GeV/c2 Work to improve understanding of detector

24.1412.5- top V/c9.9(sys)Ge)(171.2 M stat


Top Mass using b-tagging Top Mass using b-tagging Identifying a b-jet has a great impact:

Smaller combinatorics → improves the mass resolution by ~10 %

Reduction in background→

S/B = 3, increase by 300%

Allow to loosen the 4th jet

selection cuts ( 40% more events)

In 57.5 pb -1 there are 11 candidates with at least one jet tagged as a b-jet

Mtop with b-tagging is coming…


Run I Mass: lepton+4 jets Run I Mass: lepton+4 jets eventsevents

Similar with Kondo’s method, uses full set of event observables

Define a signal event probability

Define a background probability

Build an event probability

where Mt,c1,c2)

Build a likelihood L(), minimize –lnL() to get c1, c2 and Mt

),( topitt

MxP

)( ibkg xP)(),();( 21 ibkgtopi

tti xPcMxPcxP

i-th event observables

Transfer fn: resolutions, reconstruction effects

)y,x(W)q(f)q(fdqdq);y(d1

)x(Acc);x(P 2121n

Matrix Element PDF’sAcceptance

Measured to be estimated

LO ME used, 4 jets required exclusively, additional cut on background

probability (to improve the sample purity)


Run I: Preliminary resultRun I: Preliminary resultD0 Run I Statistics [PRD 58(1998), 052001]

Events 91→ 71 with exactly 4 jets → 22 after probability cut-log(likelihood) vs Mt likelihood vs Mt

2top GeV/c 4.0(syst)(stat) 3.6180.1m

Stat : 5.6 GeV from PRD 2001improvement on the statistical

uncertainty (~2.4 stats)

Run I D0 lepton+jets:173.3± 5.6(stat) ± 5.5 (syst) GeV/c2


Summary & ConclusionsSummary & ConclusionsTop physics is extremely rich and has a great potentialMany top analyses are in progress

we re-established the benchmark top quark measurements we are getting close to Run I precision

Improvements are underway Better detector understandingIncrease the tagging efficiencies of b jetsInclude forward leptons

We are enthusiastic about the top physics prospects at the Tevatron until first LHC resultsExpect results from larger samples soon

Many measurements will supersede those of Run I

Test the Standard Model to even greater precision


Top Physics Prospects for 2 Top Physics Prospects for 2 fbfb-1-1

Measurement Est. Uncertainty Tests Mt 2-3 GeV/c2 Indirect MH

tt 7% QCD Couplings [ll/l+j] 12% Non-SM Decays [B(t→Wb)/B(t→WX)] 2.8% ‘’ [B(t→Wb)/B(t→Xb)] 9% ‘’ [B(t→Wlong)] 5.5% Non-SM Coup. [B(t→WV+A)] 2.7% W helicity [B(Z’→t t)] ~90 fb Exotics

tbX+btX 24% Observe single top t→Wb26%Vtb 13% CKM Matrix


End of talk : Backup SlidesEnd of talk : Backup Slides


Top Mass TemplatesTop Mass TemplatesReconstructed top masses from data are compared to parameterized templates of top and background Monte Carlo for masses (150, 200) GeV

Use a continuous likelihood method to extract top mass and statistical uncertaintyThe bump in the background shape around 130 GeV is due to the kinematic selection of the events

signal

background


Top Dilepton KinematicsTop Dilepton Kinematics


ConstraintConstraint M MHiggs Higgs with awith a M Mtoptop and M and MWW

DØ / CDF

Run 2aGoal


Direct Higgs Search


Single TopSingle Top

2.44 ± 0.12 pb ?Steltzer, et al. ‘98

0.88 ± 0.12 pb ? Smith/Willenbrock ‘96

s<0.1 pbTait ‘99

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Top: latest results from Tevatron – cross-section and mass